The Ca²⁺ concentration in vitro impacts the cytokine production of mouse and human lymphoid cells and the polarization of human macrophages

Abstract

Various aspects of the in vitro culture conditions can impact the functional response of immune cells. For example, it was shown that a Ca2+ concentration of at least 1.5 mM during in vitro stimulation is needed for optimal cytokine production by conventional αβ T cells. Here we extend these findings by showing that also unconventional T cells (invariant Natural Killer T cells, mucosal-associated invariant T cells, γδ T cells), as well as B cells, show an increased cytokine response following in vitro stimulation in the presence of elevated Ca2+ concentrations (approx. 1.8 mM). This effect appeared more pronounced with mouse than with human lymphoid cells and did not influence the survival of the lymphoid cells. A similarly increased cytokine response due to elevated Ca2+ levels was observed with primary human monocytes. In contrast, primary human monocyte-derived macrophages, either unpolarized (M0) or polarized into M1 or M2 macrophages, displayed increased cell death in the presence of elevated Ca2+ concentrations. Furthermore, elevated Ca2+ concentrations promoted phenotypic M1 differentiation by increasing M1 markers on M1 and M2 macrophages and decreasing M2 markers on M2 macrophages. However, the cytokine production of macrophages, again in contrast to the lymphoid cells, was unaltered by the Ca2+ concentration. In summary, our data demonstrate that the Ca2+ concentration during in vitro cultures is an important variable to be considered for functional experiments and that elevated Ca2+ concentrations can boost cytokine production by both mouse and human lymphoid cells.

The role of nanopores constructed on the micropitted titanium surface in the immune responses of macrophages and the potential mechanisms

“…46 IP3 can bind to IP3 receptors (IP3R) on the ER membrane and activate Ca 2+ pumps, thus releasing Ca 2+ from the ER lumen to the cytoplasm. 47,48 Excess Ca 2+ in MF cytoplasm can induce inflammation, 47,48 and Ca 2+ triggers calcineurin (CN) to suppress the activation of NFAT. 49 Consequently, the decreased expression of IP3 in the TA group lowers intracellular Ca 2+ levels, which in turn contributes to the dephosphorylation of NFAT and its translocation to the nucleus through calcineurin (CN).…”